Investigations are being made into the stereospecificity of certain enzyme-catalyzed reactions involved in biosynthesis of organic compounds, largely through the synthesis of stereospecifically deuterated molecules to serve as substrates. Problems to be studied during the coming year include: 1. Stereospecificity of methyl migration in valine biosynthesis. Methyl-labelled acetolactate will be used to determine whether the rearrangement induced by isomeroreductase produces a single configurational isomer of dihydroxyisovaleric acid. 2. Stereospecificity of the dehydrogenation process in the metabolism of valine and isoleucine. 3. Absolute stereospecificity of the hydroxymethyl transferase reaction in hydroxymethylserine. 4. Absolute stereochemistry of the hydrogen migration step in the ethanolamine ammonia lyase reaction. 5. Determination of absolute configuration of the alkyl-substituted malic acids biosynthesized by acetyl coenzyme A condensations.